Income Taxes - Significant Components of Company's Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Millions	Sep. 26, 2015	Sep. 27, 2014
Deferred tax assets
Net operating loss carryforwards	$ 45.4	$ 54.2
Capital losses	25.7	22.3
Non-deductible accruals	16.3	16.8
Non-deductible reserves	26.8	27.1
Stock-based compensation	24.3	25.0
Research and other credits	14.5	12.3
Nonqualified deferred compensation plan	11.3	13.7
Other temporary differences	10.2	11.6
Deferred tax assets, gross	174.5	183.0
Less: valuation allowance	(60.9)	(62.8)
Deferred tax assets, net	113.6	120.2
Deferred tax liabilities
Depreciation and amortization	(1,171.5)	(1,314.6)
Debt discounts and deferrals	(100.1)	(120.9)
Debt issuance costs	(1.4)	(6.8)
Investment in subsidiary	0.0	(13.9)
Deferred tax liabilities, net	(1,273.0)	(1,456.2)
Net deferred tax liabilities	$ (1,159.4)	$ (1,336.0)